18
PART III : ALIGNMENT
Advantage: For visual observing, the mount does not need to be polar-aligned accurately.
Preconditions: Small cone error in the telescope-mount setup.
Rules for choosing alignment stars:
• The deviation in R.A. of the two alignment stars should not be too small or too close
to 12 hours; the recommended deviation is between 3 hours and 9 hours.
• If there is cone error in the telescope-mount setup or if users are not sure about it, it is
recommended to choose two alignment stars that are on the same side of the meridi-
an. The absolute values of the two alignment stars’ declination should should deviate
between 10 to 30 degrees.
Note:
If the polar alignment of the mount is good, it is not necessary to choose “
2-Star
alignment
” to align the mount, use the “
1-star alignment
” instead.
Advantages:
• Good pointing accuracy; even when the telescope-mount system has cone error.
• For visual observation, the mount does not need to be accurately polar-aligned.
Preconditions: The skies of both sides of the meridian are clear of obstructions.
Rules for choosing alignment stars:
• The 3 alignment stars should be spread out on both sides of the meridian.
• For the two alignment star on the same side of the meridian, their R.A. deviation
should be greater than 3 hours, and the absolute value of the difference between the
two alignment stars’ declination should be between 10 to 30 degrees.
( 10° < |Dec1 – Dec2| < 30°)
• If there is cone error in the telescope-mount setup or users are not sure about it,
avoid the situation that all 3 alignment stars have small declination (close to the celes-
tial equator).
Note:
If users are sure that there is no (or very small) cone error in the telescope-mount
system, then it is not necessary to choose the “
3-star alignment
” to align the mount. Use
“
1-star alignment
” or “
2-star alignment
” instead.
The “
Brightest Star Alignment
” is designed for entry level users who cannot identify stars in
the night sky, and the “
2-Star alignment
” is for users who know the names of the stars in
the night sky. Both alignment methods provide the same level of precision.
Rules for choosing alignment stars:
• It is recommended that the altitude of the two alignment stars are between 15 and 60
degrees and the deviation in altitude is between 10 and 30 degrees.
• The azimuth deviation of the two alignment stars can be between 45 and 135 de-
grees, it is best to be close to 90 degrees.
2.
Equatorial Mount with 2-Star Alignment:
3.
Equatorial Mount with 3-Star Alignment:
4.
Alt-azimuth Mount: